Question

I think ------silly------you not to forgive others for their mistakes.

A it, for B it's of C that's of D it's for

Answer 1

I think 是主谓结构，后接一个宾语从句。
It is adj. for/ of sb (not ) to do sth.这是个固定句型。中间的for /of的选择。
当前面的形容词用来修饰后面的不定式这个动作时，用for;
当前面的形容词用来修饰时，用of.这时可以说成：sb be adj.
句中的silly是用来修饰you的，可以说成：You are silly
选择B。

Answer 2

b